Much attention has been given recently to the matter of converting solar energy to a useful form so as to reduce the dependency of mankind on fossil fuels and nuclear energy. It is estimated that several thousand patents have issued in the last ten years as solutions or partial solutions to the solar energy converting problem. Two general approaches to the solar energy conversion problem seem to dominate the existing literature and practice on the subject.
In one form, collectors are provided for mounting on the ground or on the roof of a dwelling. The collectors consist of large reflectors covering a large area of the dwelling roof, the reflectors being curved to focus the sun's rays onto a tube containing a fluid to which the solar energy is transferred. The tubes of a plurality of collectors are interconnected and the fluid contained therein is directed principally to a central heating area. Provision may be made for converting some of the energy contained in the fluid to electrical energy so as to satisfy some of the energy requirements of the resident other than heat.
The system described above has a number of disadvantages. It is necessarily a low temperature system without any capability of storing significant quantities of energy for use on days when the sun is not shining. The low temperature heat is efficient only for space heating. As a consequence, it is at best only a supplement to the forms of energy currently in use and is not suitable for year-round supplying of energy.
Additionally, the requirement of transmitting the energy via fluid passage through substantial lengths of tubing is disadvantageous in that the exposure of the tubing, through insulated, to ambient temperature results in substantial heat loss. These heat losses prevent the system from attaining simultaneously the high temperature and high efficiency needed for meeting the full energy needs of the house.
Finally, the system does not easily admit of the tracking of the sun by the collectors and thus the sun's rays do not efficiently and directly impinge upon the collector system except during the limited period of time.
Another form for solar energy conversion has been called a power tower. The power towers which have been principally disclosed consist of a plurality of reflectors mounted on the ground or on terraced structures built for that purpose to cover a very sizeable area. A central target is provided and the reflectors are arranged to receive energy from the sun and direct it to the target in the tower. Usually, provision is made for driving the reflectors either individually or in groups so as to track the sun as it passes from horizon to horizon.
The power tower is a much more practical type of energy converter in the utilization of systems for tracking the sun and in the reflecting of radiant energy directly to target as contrasted to the utilization of a fluid medium as described above.
For the homeowner, the power tower has not been a feasible solution to the use of solar energy. There has been disclosed no practical way of collecting the solar energy and directing it to a target from which the heat can be extracted. For example, it is impractical to have a tower placed in the middle of the owner's property to receive the radiant energy from the collectors. No practical way has been disclosed for converting the energy received from the target to useful energy which the homeowner can use year-round.
Finally, for the power tower to be a successful energy-converting system, the radiant energy passing through the atmosphere from the collectors to the target would be of such great intensity that it would endanger the living things in the area.
An objective of the present invention has been to provide a solar energy system principally for use with a dwelling for human beings, the solar energy system providing efficient utilization of solar energy throughout the year. In most areas of the country, complete home energy needs can be provided year-round without a back-up system.
This objective is attained in part by a collector array, mountable on a roof top, with means at the collector for concentrating the impinging solar energy and transmitting it in a compact form to a nearby target. The collectors are preferably mounted on a plurality of spaced bars or carriers which are angulated in such a way as to most efficiently capture the sun's rays and direct them efficiently to the target. Means are provided for rotating the carrier bars about first axes and rotating the reflectors about second axes lying in planes perpendicular to the first axes so as to track the sun as it passes from horizon to horizon and as it moves between its highest and lowest points with respect to the horizon.
Preferably, the collector reflectors and/or lenses are mounted above the carrier bar so as to create a substantially unobstructed path of the sun's energy onto the collector system and to the target.
The collecting concentrating and transmitting system permits the disposition of a target at about ground level and quite close to the dwelling with which the system is used. Several advantages are derived from this feature. The path of the concentrated sun rays between the collector and the target can be effectively shielded so as to eliminate the possibility of living things passing through the path of those rays. The target can be located quite close to the storage room as well as other accessory elements such as electrical generating systems so that loss of heat through convection is minimized.